Rapid tool manufacturing techniques such as Selective Laser Sintering, Stereolithography, and rapid prototyping are the techniques generally used for the rapid recreation of parts. However, these techniques create parts that are generally suitable for use in space and design studies and not for real world applications. Furthermore, these tool manufacturing techniques generally require soft tools, molds and casting to often create plastic type fabricated parts with many inherent problems since these techniques do not use the same materials as the original part to be recreated. The prior known manufacturing techniques are prone to create fabricated parts different from the original parts. For example, if one were to use stereolithography to manufacturer a plastic fan wheel, the resultant part would have different surface characteristics and weights than an aluminum flywheel that is desired to be duplicated. Important characteristics such as flow separation points, efficiency of operation, pressure ratio over the blades, mass flow therethrough, will be different. Also plastic parts created by stereolithography cannot operate in high temperature environments. Thus, plastic car exhaust parts created by stereolithography manufacturing techniques would not be useful for the high temperature environments of vehicle engine emissions. Furthermore, these plastic fabricated parts would have a very short lifespan in chemically active environments.
Using a casting manufacturing technique creates a part having a homogeneous uniform material. Thus, casted parts exhibit uniform mechanical and thermophysical properties throughout their structure. Casted parts cannot have materials with graded(varied) compositions. Casted parts may crack and break down in applications where increased strength characteristicsare needed such as along the center axle region of the fly wheel example.
The prior known techniques are not useful for refurbishing damages to existing parts(e.g. camshafts) nor for fixing localized damage such as scratches on existing parts. Furthermore, the known manufacturing techniques are not usefull for providing any wear resistant coatings to existing parts.
The prior known techniques involve a number of steps for parts fabrication, including sintering, mold and die casting, using material mixtures containing materials other than the original material, or using support structures during fabrication.
Many U.S. patents have been proposed but fail to overcome all the problems presented above. See for example: U.S. Pat. Nos.: 5,189,781 to Weiss et al.; 5,314,003 and 5,393,613 to Mackay; and 5,316,580 to Deckard employ predeposited powder in a flat bed which is leveled in a form and melted by a scanning laser beam; 5,384,523 to Masuda; 5,385,780 to Lee sinters polymer powder; 5,398,193 to de Angelis requires masks to make parts, also, the process creates sharp boundaries between two different materials; 5,475,617 to Castonguay; and 5,622,577 to O'Connor requires two different processing chambers, and also employs a predeposited powder. Although, in recent years, several processes were developed which enable the user to fabricate parts from stronger materials than commonly used in conventional Rapid Prototyping processes, or even to fabricate parts with a metal content. These processes do not solve all of the problems stated above. Some of these techniques can take as many as nine(9) or more steps to fabricate the final part. From an end users point of view, this is a very time-consuming and costly option.
Several related but overly complex tools have been suggested in the past. See for example 5,239,160 to Sakura et al.(Five-Axis Table); 4,726,715 and 4,803,335 to Steen et al.(powder delivery); 4,724,299 to Hammeke(Laser Spray Nozzle); 5,453,329 and 5,477,025 to Everett et al.(Powder Nozzle and Abrasive Particle Deposition). These inventions present an "overkill" in terms of their operation, usage, maintenance, and operating costs.
The Mechanical Engineering Magazine March 1997 edition describes many of the prior art techniques. Ashley, Steve, "From CAD art to rapid metal tools", Mechanical Engineering, March 1997, pages 82-87, introduces a similar process, called LENS(Laser Engineered Net Shaping) by Sandia National Laboratories. Major limitations of LENS are the restrictions of being able to fabricate extruded parts only(having no undercuts nor overhangs. Also, the process is based on using four powder delivery nozzles. Rapid Manufacturing is capable of creating undercuts and overhangs, also, the alignment of the powder delivery to the focussed laser beam is easier as the powder is delivered by one nozzle only. In addition, the introduction of turbulences into the shield gas flow, due to aligning and interaction of multiple shield gas jets is eliminated. The LENS-process is distinctly different from the Rapid Manufacturing process of the subject invention described here, in that it requires an enclosure around the laser beam -material powder interaction region to create a non-oxidizing environment. The preferred embodiment for LENS appears to be Argon shield gas, whereas the Rapid Manufacturing of the subject invention process has worked successfully with different shield gases, such as Helium and Nitrogen. Also, for the Rapid Manufacturing process of the subject invention, it is optional to use the same material as base substrate and for the deposition whereas LENS apparently is preferentially used for same material combinations. Finally, LENS so far does not incorporate real-time sensor feed back.
None of the prior art know to the subject inventors comprises all the desirable features of: full fabrication out of the original material, fabrication in one step, without a dependence on support structures.